Terminal adapters can be used for heavy-duty industrial plug connectors in the automotive industry, machine-building industry, in plant construction and in measuring and control engineering. Terminal adapters integrate plug-connector contact inserts and downstream series terminals into one space-saving, individual connection element. When used together with the corresponding housing, contact inserts provide for an industry-compatible leading-through of lines through control cabinet walls.
With regard to the conductor connections in the series terminal section, different connection techniques can be used for the 6 to 24-pole terminal adapters to facilitate a simple and rapid assembly. Different connection techniques can also be used for the contact inserts in the different performance classes including screw, crimp or insulation-displacement connections, the contact inserts being composed of female and male inserts.
Ground conductors are frequently used in electrical connection systems. These ground conductors are also referred to as earth potential. In electrical systems, the ground conductor has the task of protecting people from dangerous contact voltage and the system from further damage. The ground conductor is installed with the purpose of forming an electrical connection between the outer metallic housing of electrical equipment and the earth. In a fault scenario, when the electrical voltage of the supply system reaches the external components of the electrical equipment, the short circuit across the ground conductor serves to ensure that the voltage between the device housing and earth becomes zero.
At the same time, the electrical supply voltage is tripped by the short-circuit current that is produced. This very quickly isolates the defective equipment from the electrical supply voltage.
German regulations stipulate that ground conductors be identified by the color green/yellow. Cable connections leading to equipment having a metal housing and grounding-contact connection lines require that the ground conductor be incorporated therein in a cross section suited for the occurring amperage and that it match the energized lines. At grounding-contact plug connections, the ground conductor is connected to the grounding contacts which provide for an uninterrupted connection of the ground conductor.
Cited here exemplarily are terminal adapters (HC-KA) and contact inserts (HC-B) which are equipped with an integrated PE ground conductor system. See the product catalog “PLUSCON 2002” TNR 5123513/01.04.02.00 of the firm Phoenix Contact GmbH & Co KG, Blomberg.
Multipole electrical plug connectors having an insulating body supporting the electrical contact elements that has a connector side and a conductor connection side are described, for example, in the German Examined Application DD 242 312 A1 or the German Patent DE 82 15 606, or are described in the German Patent DE 37 35 312. In the case of these plug connectors, the ground conductor system is typically constituted of an electrically conductive, metallic fixing bracket upon which a screw connection is configured for receiving the ground conductor, the fixing bracket including a retaining member having a one-piece clip and being provided with a screw connection. The metal part, which is thin due to the sheet thickness typically used for this purpose, is provided with a thread for receiving the screw connection that can easily be overtightened in response to a forceful actuation. The screw connection itself is constituted of a metal screw and a metal disk, which is also described as a pressure plate and, in the square plate-like form, is umbrella-shaped. The metal screw and the small metal plate can be corrosion-protected by a galvanically applied nickel or tin coating.
In addition, from the German Utility Model Patent 81 25 854 U1 for connecting a conductor at one individual plug-in contact, it is described that it is necessary to eliminate the disadvantageous overtightening of the terminal screw when screwing the same into thin sheet metal when connecting relatively large conductor cross sections, and that the disadvantage is eliminated in the internal thread region through the use of a double sheet metal layer or by lengthening the thread by providing a raised rim at a cage clamp, as is described in German Application DE 103 15 668 A1 or the German Examined Application DE 1 690 745 B for connecting the conductor to a conductor bar. Moreover, in place of double-layer cage clamps, the German Patent DE 37 32 267 C1 or the Swiss CH 392 658 discuss also using cage clamps fabricated from solid material especially for connecting electrical conductors to thin sheet-metal strips.
Vibrations have a detrimental effect when working with electrical plug connectors that are equipped with a PE ground conductor system having this aforementioned conventional screw connection technology. A vibrational stress can induce loosening of the clamp connection between the ground conductor and the screw connection, necessitating a retightening of the clamping screw and thereby giving rise to the overtightening problem described above. The conductors to be connected are, therefore, provided with ring or cable lugs that are fastened to this screw connection in a complex process that requires taking the conductor length into account. This type of fastening process is time-consuming since it requires crimping-on the conductor, and it is not operator-friendly since it requires completely unscrewing the fastening screw. The ring lugs of the particular conductor cross section frequently do not match the fastening screw diameter.
A further drawback is that, in the context of the aforementioned screw connection technology, the minimal amount of corrosion protection provided by galvanic coatings can have a negative effect on the long-term functioning of the screw connection. When installing the ground conductor, the clamp connection can become damaged at the surface by the tool to be used.
However, due to the small unit volume of such plug connectors, the connection device for a ground conductor is not able to be readily equipped with a cage clamp. Further designs would be required to permit the use of a cage clamp. For these reasons, however, methods heretofore have not provided that this ground conductor connection point be equipped with cage clamps for connecting the ground conductor. Surface damage to the clamp connection can produce oxidation. Such oxidation increases the risk of rusting and the consequences thereof. These consequences can include a poor electrical conductivity of the clamping point for the ground conductor, for example.
In addition, it would be beneficial to rationalize the production of the metal part, for example, of the fixing bracket, by saving a manufacturing step. Such a rationalization could eliminate the need for the threaded bore in the metal part of the fixing bracket for the screw connection, thereby saving a manufacturing step.